Clinical characteristics and antimicrobial susceptibility of Klebsiella pneumoniae, Klebsiella variicola and Klebsiella quasipneumoniae isolated from human urine in Japan

Introduction. The three Klebsiella species K. pneumoniae, K. variicola and K. quasipneumoniae are difficult to distinguish, owing to their similar biochemical properties, and are often confused in medical practice.Gap statement. There is a scarcity of data comparing the clinical characteristics and antimicrobial susceptibility of K. pneumoniae, K. variicola and K. quasipneumoniae. We believe that knowledge of the characteristics of each species will help in their better identification. Further, knowing the antimicrobial susceptibility of the species will help physicians in prescribing an effective treatment course for Klebsiella infections.Aim. This study aimed to determine the clinical characteristics and antimicrobial resistance of K. pneumoniae, K. variicola and K. quasipneumoniae isolated from human urine samples.Methodology. This study included 125 K. pneumoniae strains isolated from human urine samples. Multiplex polymerase chain reaction was performed to identify K. pneumoniae, K. variicola and K. quasipneumoniae. We retrospectively investigated the patient background, complications of bacteraemia, antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL).Results. We identified 84 (67.2 %), 31 (24.8 %) and 10 strains (8 .0%) of K. pneumoniae, K. variicola and K. quasipneumoniae, respectively. There was no difference in patient background and frequency of bacteraemia complications among these species. K. pneumoniae was significantly less susceptible than K. variicola to ampicillin/sulbactam (P=0.03) and piperacillin (P<0.01). Furthermore, K. pneumoniae (79.8 %) was less susceptible to trimethoprim/sulfamethoxazole than K. variicola (96.8 %) and K. quasipneumoniae (100 %). There were nine ESBL-producing strains (7.2 %), all of which were K. pneumoniae.Conclusion. There was no difference in patient background and frequency of bacteraemia complications between K. pneumoniae, K. variicola and K. quasipneumoniae isolated from urine. The three Klebsiella species showed a varying extent of antimicrobial susceptibility and ESBL production, and accurate identification is needed to understand the epidemiology of these species.